Production of casein



Patented Nov. 13, 1945 PRODUCTION OF CASEIN William F. Oatman, Geneva, Ill..- assignor to Hercules Powder Company, Wilmington, DeL, a

corporation of Delaware No Application February 18, 1942,

- Serial No. 431,340

8 Claims. (CL 260-120) This invention relates to the production of casein from skim milk powder and more particularly to the production of acid or rennet casein from spray or roller-dried skim milk powder.

The production of casein from skim milk powder instead of from liquid skim milk has been found to be desirable in particular commercial plants during periods of low milk volume in that area, during periods of low market price for the powder, and in areas where the transportation of the whole skim milk is diflicult or expensive.

For the purposes of human consumption, skim milk powder has an advantage over fresh milk in that the curd from the powder is much softer than the curd from fresh milk and hence is more easily digested. This same principle of produc-' ing soft curd is a dimculty which had to be overcome in order to make possible the use of skim milk powder for the commercial production of casein. Skim milk powder has been mixed with water to give a percentage solids content comparable to skim milk and the casein precipitated with sulfuric acid at temperatures and acidities which would have produced tough curd with skim milk.- However, the curd in this case is soft and entirely unsuited for casein for ordinary commercial uses.

Now, in accordance with this invention it has been found that a tough casein may be produced from skim milk powder which has been diluted with skim milk or with mixtures of skim milk and water. It has been found that the most desirable product is obtained when the skim'milk powder is diluted with from about 10 to 20 times its weight of skim milk or mixtures of skim milk and 7 water. The skim milk may be diluted with vary-- 'ing amounts of water, but it has been found most desirable that the amount of water should not exceed its equal weight of skim milk. In the present specification and in the appended claims, the term "skim milk" as applied to skim milk in the liquid state is intended to refer to both the undfluted skim milk and the smm milk which has been diluted with up to an equal weight of water.

The resulting mixture of dried skim milk powder in skim milk, with ,or without additional water, may be precipitated with any of the ordinary casein precipitating agents such as rennet or an acid such a sulfuric acid, hydrochloric acid, lactic acid, sour whey, etc. The conventional precipitating conditions-may be used, but

it has been foimd to be preferable to employ par-.

- of 0.1% to 0.5% by weight of calcium chloride or i Thus, when rennet is used as the precipitating agent, best results are obtained by precipitating the casein from the blend of dried skim milk powder and skim milk at a temperature of about F., the rennet being used in such a proportion as to complete setting to a firm curd in about 15 minutes, At the expiration of this time, the curd is separated from the whey in the usual manner, washed and the casein recovered therefrom in the conventional way. The set of the curd should be considerably firmer than with skim milk alone, this being due to the high solids content of the mixture of dried skim milk powder and skim milk. The curd may be washed in the normal manner, i. e., once with lukewarm water, then with water at about 150 F'., and then with 'two washes of *cold water. The resulting casein is comparable to rennet casein from fresh skim milk, particularly as regards free acidity, ash content, odor, and dirt content.

When a mineral acid is used as the precipitating agent, such as for example sulfuric acid, best results are obtained by precipitating at a temperature of about F, at a pH of from about 5.0 to about 52. Following precipitation under these conditions, the curd is washed and the casein recovered in the conventional manner.

While spray-dried skim milk powder appears to give the highest quality casein product, the process has been successfully carried out using roller-dried skim milk powder.

The yield of casein in accordance with'the process of the present invention is substantially normal, 1. e. equal to that which should be obtained ifiresh skim milk in comparable amount were employed as the raw material. Yields of from 2.5% to 3.0% were obtained based upon the weight of the fresh skim milk equivalent to the skim milk and dried skim milk employed as the raw materials.

It has also been found desirable in order to aid in the coagulation of the mixture oi.v skim milk powder and skim milk with or without water to add a small amount of calcium salt. Addition other calcium salt was found to aid the coagulation,

Oun es Of rennet extract at a temperature of 95 'centaaeotash.

i iandthesettinstoanrmcurdwasaccomwh'ew ndrennetandieoover-ingn-omthemixplishedinaboutid utes. Attheexplration tureprecipltatedcaseininthetormotsnrm oithistime,thecurdwasseparatedtromthe whey in the usual manner.-then washed with lukewarm water.washedaaainwith' wateratiliil' R, andflnallywith two cold water washes. The

qualiw'ot the rennet casein produced, particularly as resards tree acidity, ash content, odor,

anddirtcontentwascomparabletothebestqual l- Example II Hitapoundsot weremixedwithmoopoundsorireshskimmiik. 'i'hecurdwasprecipitstedwithsulfuricacid whichwasaddedlmtiltheplioithemixture reached5.0andatatemperatureot1401". The curdwasseparatedandwashedinthesameman- .nerasinI. Thecurdproducedwas quite iirm.

1 Empls Ill Six hundred pounds of roller-dried skim milk powder were mixed with 8,000 pounds of fresh skimmilk. Thecurdwasprecipitatedwith 16 mmoesotrennetextractstatemperstmeotild" Eandthesettingtoaflrmcurdwassccomplishedinaboutifiminutes. Theseparstionand washinswerecsrriedoutasinlxsmpleL Whilethewioroitheproductwasnotasdesirableasthstobtainediromthespray drledskim:

milk powder. the odor and dirt content were aboutthesameandtherewasaslishtlyiessneri'mplelv l'itiw pounds or roller-dried skim milk powd were-mixedwithmpoundsoiireshskimmilk andbdflpoundsotwater. 'I'hecurdwssprecipitated with sulfuric acid which was added rmtilthepHreaehediiJ. Theseparationand washingwasearriedoutasinzxamplel. The resuitantcurdwastouah.

'Ihe present invention enables the osseinpmducertooii'setfluctuationsinnormalskimmiik volumebytheuseotdriedskimmiikpowder whenthevohzmeolskimmiikislowinthearea;

'I'hedriedskimmilkpowdermaybestoreduntil such periods occur. Also, in the costofhnulinzskimmilkmaybesohighasto makeitmoredesirahletomakedrledskimmilk.

powderandahipitinsteadoftheskimmiikitsoli. l urthermore,bytheuseofthisprocess,thereis -a higher concentration of solids in the wh'ey and thereiorethecostotevaporationtorecoverthue solidsislessatthecaseinplant. Numerousother advsntagesottheprooessoverthe presentinventionwiil be apparentto thoseskilled inth'e art. WhatIclaimanddesiretoprotect-byhetters Patentis:

1. 'Iheprocessoiobtainingcaaeininthetorm oi'aflrm curdirom dried skimmilkpowder which consists inmixing dried skim milk powder with spray-dried skim milk powder tothemixtur'e acasein-precipltatin: cent se-' lectedimmthesroupoonsistinzotaeidssour wheyJndr-ennetandrecoveringtromthemixpreoipltatedessein in me tormot giirm consists in mixing spray-dried skim powder with fresh skim milk, precipitating tothemixtureacaseinprecipscent selected from the group consistsmrrwhezandrennet, and recovermixtureprecipitated caseininthe oiaiirmcurd.

processoiobtaininzcaseininthetorm curd tromsprey-dried skimmilkpowwhich inmixing spray-dried skim timesitsweightottreshskimmilhprecipitatine by adding to the mixture at casein-precipia:ent selected from the group consisting 5.111eprocess d obtainingcaseininthetorm otaflrmcurdfi-omskim consistsinmixingskim aboutlotoaboutfliltimes skimmilkm'ecipitating mixtureacasein-precipita ingiromthemixturepred tormodalirmcurd.

8.111s process ot oiztaining casein in the milk milk tion iozmofaflrmourdtromdriedskimmiikpowder ireshskimmiihprecipitatingcsseinbyadding to the mixture. a. casein-precipitating agent selectedtromtlmgroupconsistlnsotacide-sour whichconsistsinmixingdriedskimmiikpowder 'wnmmr. 04 1mm derwithiromaboutiiltoaboutzd powder which powder with from its w ht 0! fresh casein by adding to the acid, and recovertated casein in the 

